引入 FOREIGN KEY 约束...可能导致循环或多个级联路径 - 实体框架

Question

I'm new to Entity Framework and I've tried to fix this for multiple hours now but I'm now at a complete loss.

Could anybody be so kind to point out what I'm missing here?

I get this error when I try to run Update-Database:

Introducing FOREIGN KEY constraint 'FK_ContainerActies_Locaties_LocatieId' on table 'ContainerActies' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints. Could not create constraint or index. See previous errors.

I try to turn the cascade delete off in OnModelCreating:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<ContainerActie>()
      .HasOne(c => c.Locatie)
      .WithMany(c => c.ContainerActies)
      .HasForeignKey(c => c.LocatieId)
      .OnDelete(DeleteBehavior.Restrict);
}

But it doesn't seem to have any effect.

public class ContainerActie : SQLModel
{
    [Category("DB")]
    [Key]
    public int ContainerActieId { get; set; }

    [Category("Info")]
    public Container Container { get; set; }

    [Category("Info")]
    public Actie Actie { get; set; }

    [Category("Info")]
    public Relatie Relatie { get; set; }

    [Category("Info")]
    public int LocatieId { get; set; }

    [Category("Info")]
    public Locatie Locatie { get; set; }

    [Category("Info")]
    public DateTime DateTime { get; set; }
}

public class Locatie : SQLModel
{
    [Category("DB")]
    [Key]
    public int LocatieId { get; set; }

    [Category("Info")]
    [Required]
    public string Naam { get; set; }

    [Category("Info")]
    public string? Adres { get; set; }

    [Category("Info")]
    public string? Gemeente { get; set; }

    [Category("Info")]
    public string? Postcode { get; set; }

    [Category("Info")]
    public string? Tel { get; set; }

    [Category("Info")]
    public string? Commentaar { get; set; }

    [Category("Info")]
    public List<ContainerActie>? ContainerActies { get; set; }
}

Answer 1

这是因为外键LocatieId不可为空，如果该键不可为空，则必须删除相关对象，循环关系不允许这样做。